Helixing lathe having automatically changeable chucks



May 11, 1965 A. J. vRsl-:CKY D 3,182,425"

HELIXING LATI-IE HAVING AUTOMATICALLY CHANGEABLE CHUCKS y Filed June 15,1962 .2 Shets-Sheet l l INVENTO aib/1 y I 715196.35 y

A'IITORNEY May 11, 1965 A. J. vRsEcKY HELIXING LATI-IE HAVINGAUTOMATICALLY CHANGEABLE CHUCKS Filed June-15, 1962 2 Sheets-Sheet 2United States Patent O 3,182,426 HELIXING LATHE HAVING AUTOMATICALLYCHANGEABLE CI-IUCKS Anthony J. Vrsecky, Winston-Salem, N.C., assigner toWestern Electric Company, Incorporated, New York,

N.Y., a corporation of New York Filed June 15, 1962, Ser. No. 202,725

6 Claims. (Cl. 51-95) This invention relates to a helixing lathe havingautomatically changeable chucks, and more particularly to a helixinglathe having special chucks which are automatically changeable foraccommodating workpieces of different sizes and diameters. Thisinvention finds special utility in helixing, that is forming a spiralconductive path on, electrical resistors of the type including a thinconductive film deposited on an insulating core.

In the manufacture of electrical resistors, such as deposited carbonresistors, it is customary to provide a resistor blank having anonconductive, cylindrical core body on which is deposited a thin,conductive lm of carbon. A helical groove is progressively cut throughthe carbon lilm unti-l the resistor has been helixed to desiredresistance value. Resistors of this sort vary in physical size, usuallythose of higher power ratings being larger in over-all size and diameterthan those of smaller power ratings. Where resistors of different powerratings are to be helixed, it is desirable to provide a helixing lathethe chucks of which are readily changeable to accommodate resistorblanks of different sizes and diameters.

An object of this invention is to provide a new and improved helixinglathe having automatically changeable chucks.

Another object of this invention is to provide a helixing lathe havingautomatically changeable chucks for accommodating resistor blanks ofdifferent sizes and diameters.

It is a further object of this invention to provide a new and improvedchuck having a plurality of work holding faces which are selectivelypresentable in work engaging position.

Apparatus illustrating certain features of this invention may include apair of opposed chucks for supporting a workpiece which is to behelixed. Each of the chucks has a plurality of Work holding faces, whichmay, for example, be suitable in size and shape to accommodate resistor'blanks of ditIerent diameters. Means are provided for selectivelypresenting a work holding face of each chuck in a workpiece engagingposition. Also provided are means for cutting a helix in the workpiecewhich is supported between the chucks. y

A complete understanding of this invention may be obtained from thefollowing detailed description of a specie embodiment thereof, when readin conjunction with the accompanying drawings, wherein:

FIG. l shows a deposited carbon resistor partially in section which hasbeen helixed to desired resistance value in a helixing lathe accordingto this invention;

FIG. 2 is a schematic elevation of a speciiic embodiment ofr` thisinvention showing a resistor blank supported between chucks for rotationand for longitudinal motion .relative to a cutter whereby the blank maybe'helixed to resistance value;

V3 and 4; and

FIG. 6 shows a resistor blank supported between work holding faces ofthe chucks shown in FIGS. 2,-5, and

ICC

also the line of approach of the blank, so supported, toward the cutter.

In FIG. 1, there is illustrated a deposited carbon resistor including acore body 16 having a conductive carbon coating 17 deposited thereon. Apair of conductive caps 1S are secured about the core body in electricalcontact with the carbon coating, and a pair of leads 19 are electricallyconnected to the caps, as by welding. -In the embodiment of thisinvention described in detail below, it will be seen that this inventionproduces a helical cut 2t? in the carbon coating 17 thereby determiningthe electrical resistance between leads 19.

/Jhile this invention will be described with particular reference to thehelixing of deposited carbon resistors similar to that illustrated inFIG. 1, it will be understood that the helixing lathe according to thisinvention is a tool of generally applicability in helixing.

Referring to FIG. 2, an unhelixed resistor blank 21 is supported betweena pair of chucks 23 and 24 which are journaled forl rotation withinbearings 26 and 27, respectively. Bearings 26 and 27, in turn, aresupported on arms 2S and 29, both of which are mounted so as to beslideable along, but not rotatable about, splined guide rod 31. A pairof bearing members 32 and 33, which are mounted on frame 34, supportguide rod 31 allowing it free rotation about and translation along itslongitudinal axis.

The separation of chucks 23 and 24 is determined by the separation ofarms 28 and 129. This separation is controllable by rotating rotatablearm 36 by means of pivot shaft 37 to drive links 38 and 39 outwardly.Links 38 and 39 are pivotally connected to arms 2S and 29, respectively.Pivot shaft 37 may be rotated in either direction by power means (notshown) within a link connector 40, which is fixed to splined guide rod31.

A pair of supports 41 and 42 are mounted for free r0- tation about guiderod 31. This mounting is such as t0 prevent longitudinal sliding on theguide rod. Chucks 23 and 24 include shafts 43 and 44, respectively,these shafts, in turn, being coupled to telescoping joints 46 and 47 bymeans of universal joints 48 and 49, respectively. The telescopingjoints are connected by means of universal joints 51 and 52 to stubshafts 53 and 54, respectively. Stub shafts 53 and 54 are journaled 'forrotation within supports 41 and 42. Thus, it will be seen that rotationmay be imparted to the chucks by rotating shafts 53 and 54. Also, due tothe action of telescoping joints 46 and 47 asthey are connected betweenuniversal joints 51 and 48, and 49 and 52, respectively, chucks 23 and24 may be swung into and out of the plane of FIG.` 2 without interferingwith the rotation of the chucks.

A motor 61 is arranged to drive an elongated gear 62 which is in -meshwith a gear 63. Gear 63 is fixed to stub shaft 54, and when revolved,imparts rotation to chuck 24. Gear 63 is in mesh with a gear 66 fixed toa shaft 67, and shaft 67 is .journaled at its ends Within supports 41and 42. AV gear 68 is iixed on the other. end of shaft 67 in drivingengagement with a gear 69. Gear 69 is fixed on stub shaft53; thus,rotation imparted to elongated gear 62 by motor 61 turns chuck 24 andalso drives the above-descrlhedgear train, gears 63 and 66, shaft 67,and gears 68 and 69 to drive stub shaft S3. As mentioned above, theturning of stub shaft 53 imparts rotation to chuck 23.- This driving:arrangement for the chucks causes them to turn in the same direction toimpart rotation to resistor blank 21 supported therebetween.

A reversible motor 71 is provided with a threaded drive shaft 72 whichthreadedly engages nut 73. A drive bracket 74 is `fixed at one end tonut 73 and at its other end to support 41. Means (not sho-Wn) areprovided for energizing motor 71 alternately in either direction for agiven number of revolutions. It will be seen that enercarriage 84 intoand o-ut of the plane of FIG. 2. Carriage 84 is slideably supported onthe upper face of base 85.

Threaded shaft 86 threadedly engages dovetail 83, and when rotated (bymeans not shown), controls the position of cutter S1 toward and awayfrom blank 21'.

Carriage 84 is provided with a pair of depending threaded members 87 and88which engage threads on'a threaded shaft 89. A reversible motor 91 isconnected to threaded shaft 89 so that energizing motor 91 in onedirection or the other controls the position of carriage $54,;

and therefore the position of cutter 81, along the longitudinal axis ofblank 21V.

Carriage 84 is provided with aprojection 96 which extends in thelongitudinal direction of resistor-blank 21..

Projection 96 is provided with a series of apertures 97 spaced along itslength into one -of which a pin 8 may be` inserted. Avpair ofmicroswitches 101 and 102,-are

mounted on base 8S'so as to be actuable byfpinv 98.

Microswitches 191 and 102 may be spaced on base 85 under projection 96'as desired.

As will be more fully understood by referring to U.S. Patent 3,063,346,and assigned to the same assignee as this application, a pair ofelectro-magnets 111 and 112,' shown schematically in FIG. 2, arearranged on either side of anar-mature (not shown) on arm 28. Energizingelectromagnet 111 attracts the armature Vand v,Swings arm 28 toward theobserver of. FIG. 2; energizing electromagnet 112 attracts the armatureand swings arm 28V awayY from the observer of FIG. 2, thus separatingresistorz blank`21` and cutter 81.' Also as will be understood byreferring to the above-mentioned copending application, the energizingof *.electromagnet 112 to separate the core body and the cutter iscontrolled by means (not shown) which are sensitive to the resistorblankv Since having been helixed to a desired resistance value.

arms 28 and 29 engage the splines of splined guide rod 31, rotationimparted to `arm 28 by means of electromagnets 111 and 112 issimultaneously imparted to both'chucks Y23 and'24. y

Chucks 23 and 24 are mirror imagesV of one another; hence, the detaileddescription yof chuck 23 withreference to FIGS. 3 6, will apply equallytofchuck'24, and aV detailed description of chuck24 will beunnecessaryg. l

Chuck 23 comprises an outer lsleeve or chucking member 121 including` anenlarged portion 122 having an annularfflangel 123 thereabout. Shaft 43`suitable for reception within bearing 26 extends from enlarged portion122. A snap ring 126-which engages a groove in shaft 124Vlocks`ichuck 23within bearing 26.

within bore y132 and extendswithin enlarged portion 122. a

As best seen'in FIG. 3, when inner chucking member 136 `is in yitsleftmost position, the'inner `and Vouterwork holding-faces have a commonvertex and cooperate'to form-7,

a single, continuous, conical work holding face. though work-holdingfaces 131 and 137 are shown-as being conicaldepressions,y it will beunderstood that the shape of these work holding facesmay .be of a shapeA.suitable for engaging-any desired-workpiece. f A" spring v141 isarranged 1within bore 132 to bias inner chucking member'136 to the rightas viewedin FIG. 3.

lInner chucking member 13.6 isprovided with a radially movement of camfollower pin 146 ywhile preventingY .inner chucking member 136 fromrotating relative to outer chucking'member 121. Y

VAs best seen in FIG. 5,` cam track 148 is provided with two lockingportions, rear locking portion 156 and forward locking portion 157. Thelocking portions extend in planes perpendicular'to the longitudinal axisof the chuck and are spaced along that axis. A diagonal positionshiftingportion 158 of the cam track connects the rear and forwardlocking portions of the cam track.

Sleeve 147 (FIG. 3) is provided with a bore 161 into which is placed adetent ball 162 jand detent spring 163. A set screw 164 threadedWithinbo-re 161 applies `pressure to the detent spring to bias detentball 162 to the left. as viewed in FIG. 3. Enlarged portion 122 isprovided` with an indentation 166 for receiving detent ballv 16.2 Y.Indentation 166 is placed so as tofreceive detent ball 162 when sleeve147 yhas 'been rotated .to place cam follower `pin `146` in rear lockingportion 156. Another indentation (not shown) is provided .in enlargedportion 122 to receive detent ball 162 when sleeve 147 has been rotatedto place cam follower pin y146 injforward locking portion` 157. Thus,theV detent ball 162 serves to yieldably lock sleeve 147against'rotation when it is in either of the extreme degrees of rotationpermitted'by cam follower pin 146.

As best seen in FIGS. 3 and 4, outer chucking member 121 is dividedalong a portion of its length by a liared slot 168and inner chuckingmember 136 is divided along a portion of its length by a ared slot 169.These slots are maintained in' alignment as shown in FIG. 4 by the sidesof slot 151 acting on cam-follower pin 146.

Referring to FIGS. 2 .and 4,V a pairof chuck `shifting disks 171 and172',` having respective drive elements 17,3 and 174 "on the peripheriesthereof, `are VVmounted to be rotated by reversible motors 178' andV179, respectively. Rotation of the chucking shifting disks bringsthedrive elements 173 and 174 linto driving contact with sleevesV 147impartingV rotation thereto*y In FIG.` 4 it may be seen that driveelement 173 (drive element 174 is identical thereto), which may, forexample, be madefof rubber, is providedy with a driving surface 177V-having a length somewhat greater than;the length of the arc connectingthe extremes of rear and forwardV locking portions 156 and 157 of camtrack 148. Since motors 17S and 179,

are reversible, energizing these motors to turn'at least oney revolutionin either ,direction fwill' impar-t rotation to sleeves 147causingthernovement ofcam tracks 14S to Y' their extreme `positions ineither, direction. e

' Operation I AssumeA that-itis desired to v*helixga `deposited carbon"lresistorjblank (hereinreferredfto 'asV a large resistor blankijthecaps18 of whichare larger than the diameter!- of inner-work holdingfaces;-137. v Reversible' motors 178l f and 179 are actuated to turn onerevolution in the clockwise direction as Vviewed in FIG'. 4, causingdrive elements 173 andf174to` turn sleeves 147.. CamV tracks 143` actupon cam follower pins 114610 position inner clucking members 136 intheir retracted positions.V (solid linesV The enlarged portion 122of theouter chucking to bring carriage 84 to a leftmost position. Motor 91 isvthen reversed and carriage 84 is driven rightward until microswitch 101is actuated by pin 9S to provide a control signal for stopping motor 91.Microswitch 101 has previously been positioned so that this controlsignal occurs at a point which stops the cutter in the desired positionfor starting a helixing cut on a large resistor blank.

Motor 71 is energized to drive nut 73 to the right as viewed in FIG. 1,thereby bringing the large resistor blank into proper alignment withcutter 81 for starting a helixing Cut.

Rotatable arm 36 is rotated with pivot 37 by link connector 40 to drivelinks 38 and 39 and close chucks 23 and 24 about the resistor blankpresented therebetween by feeding means (not shown). The alignment ofslots 168 and 169 (FIGS. 3 and 4) permits leads 19 to t within thechucking members and also facilitates the feeding of the large resistorblank between the work holding faces 131 and 137. The flare of theseslots (FIG. 4) facilitates the insertion of the leads within theseslots.

With the resistor blank chucked, motors 61 and 71 and electromagnet 111are energized simultaneously. Motor 61 imparts rotation to chucks 23 and24 and the large resistor blank; motor 71 moves chucks 23 and 24 to theleft as viewed in FIG. 2; and, electromagnet 111 swings the largeresistor blank into engagement with cutter 81. Means (not shown) monitorthe resistance of the resistor blank as it is being helixed, andenergize electromagnet 112 tovwithdraw the large resistor blank fromengagement with the cutter 81 when the blank has been cut to the desiredresistance value. This withdrawing function is described in detail inthe above-mentioned, copending application. Finally, rotatable arm 36 ispivoted in a clockwise direction to separate chucks 23 and 24 andrelease the helixed resistor.

This process may be repeated to helix any desired number of largeresistor blanks. However, since the diameter and length of the largeresistor blanks is uniform from blank to blank, it will not be necessaryto readjust the position of cutter 81 or to re-energize motors 178 and179 prior to chucking each succeeding large resistor blank. Furthermore,the action of detent balls 162 in identations 166 prevents the rotationof sleeves 147 until motors 17S and 179 are energized in thecounterclockwise direction as viewed in FIG. 4.

Assume now that it is desired to helix a resistor blank of smallerwattage rating (hereinafter referred to as a small resistor blank), thecaps 1S of which are of a diameter less than the outside diameter ofinner work holding face 137.

Referring to FIG. 6, the position of the outer work holding face 131 isshown in phantom in alignment with inner Work holding face 137. This, itwill be remembered, is the position which the work holding faces assumedduring the previous operation in supporting large resistor blanks. If asmall resistor blank, for example, blank 201, were positioned within thechucks so arranged, then outer work holding face 131 would extend overan appreciable portion of blank 201. Outer work holding face 131 wouldalso extend beyond point 202 on the surface of blank 201, this pointrepresenting the spot at which it is desirable to start the helixingcut. A path 203 represents the approach of point 202 toward the fixedcutter position. This path is angular with respect to the longitudinalaxis of the chucks as it is the resultant of two motions, one motionbeing that of the chucks moving toward the cutting wheel, the otherbeing longitudinal motion imparted to the chucks by motor 71. It mayreadily be seen in FIG. 6, that path 203 passes through the outer workholding surface 131 as shown in phantom. Thus, if the inner and outerwork holding faces were to remain in alignment during the commencementof helixing blank 201, outer chucking member 121 of chuck 23 wouldinterfere with the desired approach of the resistor blank to the cutter,or, alternatively, the initial cut would have to commence at a point onthe blank undesirably nearer the center of the blank. A correspondingproblem would also arise when the small resistor blank is withdrawn fromthe cutter 81 after termination of a helixing cut near right cap 18(FIG. 6).

In accordance with this invention, this problem is overcome byautomatically changing the size of the work holding faces which engage asmall resistor blank; inner work holding faces 137 are projected beyondouter work holding faces 131 as shown in FIG. 6.

In order to change the chucks, reversible motors 178 and 179 areenergized at least one revolution in a counterclockwise direction asviewed in FIG. 4 and rotation is imparted to sleeves 147 by means ofdrive elements 174. Cam tracks 148 move relative to caml follower pins146 until the cam follower pins rest in forward locking portions 157 andthe inner chucking member is moved into the positions shown in FIG. 6(solid lines) and in phantom in FIG. 3.

Since resistor blank 202 is of smaller diameter than that previouslyhelixed, it is necessary to move cutter 81 into the plane of FIG. 2.This is accomplished by turning threaded shaft 86 as by means of areversible motor (not shown). In order to position cutter 81 at theproper point along the longitudinal axis of blank 202, motor 91 isenergized to move the cutter leftward as viewed in FIG. 2 until pin 98is left of microswitches 101 and 102 and then reversed to drive thecutter r-ightward until microswitch 102 is engaged to produce a controlsignal for stopping motor 91. Microswitch 102 (FIG. 2) has previouslybeen placed on base so that motor 91 stops to position cutter 81 at theproper position for commencing a helixing cut on a small resistor blank.

Motor 71 is energized to drive the chucks to the right, then deenergizedto properly position the chucks relative to the cutter. For convenienceof control, this starting position may be the same regardless of thesize of the resistor blank being helixed. Rotatable arm 36 is turned inthe counterclockwise direction (FIG. 2) causing chucks 23 and 24 toengage blank 201 from the feed means (not shown). Motors 61 and 71 andelectromagnet 111 are simultaneously energized to bring blank 201 intohelixing engagement with cutter 81. As described above, helixingcontinues until blank 202 has been cut to the desired resistance valueand is interrupted by the action of electromagnet 112 when this occurs.

.Successive resistor blanks 2011 may be helixed by repetition of thisprocess, it being unnecesary to change the position of the cutter oradjust the chucks until it is desired to helix a resistor of a differentsize. Detent balls 162 maintain the adjustment of the chucks until it isdesired to change this adjustment.

It is to be understood that the above-described apparatus andconstruction of elemental parts, are simply illustrative of anapplication of the principles of this invention and that any othermodifications may be made without departing from the invention.

What is claimed is:

1. In a lathe for helixing cylindrical resistor blanks of varyingdiameters,

a pair of opposed chucks spaced along a longitudinal axis for supportinga blank to be helixed, each chuck including an outer chucking memberhaving an axial bore therein and a concave outer work holding facethereon,

ank inner chucking member having a concave inner work holding facethereon slidably positioned Within the bore with the inner work holdingface facing the same direction as the outer work holding face, and

means for imparting relative movement between the inner and outerchucking members to selectively '27 i project or retract the inner workholding face relative to the outer work holding face;

a cutter; and

means for imparting simultaneous longitudinal and transverse movement tothe chucks to engage and disengage the cutter with a blank supportedbetween the chucks. Y

2. In a chuck for supporting cylindrical workpieces of differentdiameters,

an elongated outer ychucking member having a longitudinally extendingbore therein and a concave, conical work holding face on one endthereof,

an inner chucking member having a concave, conical inner work holdingface on one end thereofv and slidably positioned within the bore withthe inner work holding face facing in `the same direction as the outerwork holding face,

means for preventing relative rotation between the inner and outerchucking members,

a cam follower fixed to the inner chucking member and projectingradially therefrom,

a rotatable `sleeve surrounding the vouter chucking member and having acam track thereon the camming surface of which engages the cam follower,the carn track having angularly disposed camming surfacesthereon formoving the inner'chucking member relative to the outer chucking member,and Vhaving locking surfaces there.

on Vfor retaining either the inner work holding face or both the innerand outer work holding faces in a work engaging position.

3. A chuck according to claim 2 wherein the sleeve is provided withdetent means for yieldably locking the sleeve against rotation relativeto the inner chucking f member when the cam follower is in engagementwith either of the locking surfaces of the cam track.

the outer chucking member, which sides engage the cam follower.

6. A chuck comprising an vouter sleeve having an inwardly extendingconical end surface,

an inner sleeve slideably mounted within the outer sleeve and having aninwardly extending conical end surface,

means for positioning the inner sleeve within the outer Vsleeves so thatboth conical end surfaces `have a common vertex,V

and means for shifting the inner sleeve relative to the outer sleeve tomove theVV conical end surface of the inner sleeve beyond the end of theouter sleeve.v

References Cited by the Examiner UNITED STATES PATENTS 1,443,651 1/23Runge 51-237 XR 2,724,306 11/55 WOOdll 90f-11.46 2,773,332 12/56VBuchman et al.x 51-15 2,869,596 1/59v Latimer 1 144-209 2,959,202 11/60Sprillgae 1447-209 3,052,272 9/62 YOCk V144---2j9 3,073,363 1/63 LOfSCdt144-209 WILLIAM W.' DYER, In., Primary Examiner.y

1. IN A LATHE FOR HELIXING CYLINDRICAL RESISTOR BLANKS OF VARYINGDIAMETERS, A PAIR OF OPPOSED CHUCKS SPACED ALONG A LONGITUDINAL AXIS FORSUPPORTING A BLANK TO BE HELIXED, EACH CHUCK INCLUDING AN OUTER CHUCKINGMEMBER HAVING AN AXIAL BORE THEREIN AND A CONCAVE OUTER WORK HOLDINGFACE THEREON,